The present invention relates to electroluminescent lamps and to methods for producing them. The electroluminescent lamps are comprised of a plurality of separate films having two major surfaces, each film including one or more layers, beginning with a flexible plastic substrate. Laminating the aforesaid films under heat and/or pressure yields effective electroluminescent lamps through the employment of greatly simplified and less critical production techniques.
Flexible electroluminescent (EL) devices are well known in the art. For example, U.S. Pat. No. 4,684,353 discloses a flexible electroluminescent device including a flexible plastic dielectric substrate which is successively provided on one major surface thereof with an electroluminescent layer, a light-transmissive conductive layer, and a layer comprised of a bus electrode; in addition thereto, the opposite major surface of the plastic substrate is provided with a back electrode.
Each of these four layers is formed by successively passing the plastic substrate through appropriate coating equipment. In the production of a lamp having multiple coatings or layers, it is not uncommon to encounter registration problems which, if not resolved, lead to a considerable waste of time, money, material, and effort. This is especially so in the case of the electroluminescent and light-transmissive materials, which are the two most expensive materials employed in the laminated product.
In addition, the plastic substrate of the example given above undergoes a minimum of four coating operations which greatly increase the handling of the substrate as well as increasing the possibility of introducing production problems which will result in a defective and useless product.
Furthermore, the product produced according to the teachings of U.S. Pat. No. 4,684,353 lacks good dimensional stability and, prior to being encapsulated, does not afford protection for the electroluminescent phosphor which is sensitive to moisture; nor does it afford protection of the electrodes from contamination or oxidation.
Thus, it is an objection of this invention to provide solutions to the aforesaid production problems, while also providing a new and improved electroluminescent lamp.